Wideband code division multiple access is a scheme of wireless transmission technique proposed by the third generation mobile telecommunication system standard organization. The well-known time division multiple access (TDMA) and frequency division multiple access (FDMA) techniques are mainly used for transmitting voice and data with low rate, so they have certain limitations. The code division multiple access (CDMA) modulation technique is a new kind of telecommunication techniques used in the situation when there are a large number of system users.
The third generation telecommunication system can provide mobile users with multi-media service similar to that of the fixed network, and supports worldwide roam with good service quality. Its biggest character is that it supports wireless services with high transmission rate, such as surfing and browsing internet in wireless condition, downloading, video with high quality, audio stream service, FTP service, visible telephone and e-mail. In the third generation partnership project (3GPP) standard protocol, the R99 version can support air transmission rate as high as 2 Mbps, in the enhanced R5 version, the high speed downlink packet access HSDPA system employs the adaptive modulation code AMC and the hybrid automatic repeat request technique HARQ, so that the third generation mobile telecommunication system can support packet service with the air transmission rate as high as 12 Mbps. Because the packet service to be transmitted has very high rate, the ways of properly scheduling the packets to the air link for transmitting is an important factor in influencing the final transmission efficiency. The indexes for evaluating the packet scheduling algorithm mainly are the peak transmission rate, the extent to which the service quality QoS is met, and the fairness level of treating the packets of respective users.
In wire data telecommunication network, there has already been the technique of packet scheduling, the purpose of which is mainly to improve the transmission efficiency of network, for example, US patent application 20030103453 “System and method for managing flow bandwidth utilization in a packet communication environment” proposed a Time-Division-Queue Rate Control Scheme (TDQ-RCS) to resolve the problem of packet scheduling in wire data telecommunication. However, since in the wire telecommunication system, the analysis on packet scheduling, generally speaking, is based on two kinds of channel states, which are the availability of channel and the non-availability of channel, rather than the channel quality, while there may be many kinds of channel states in the wireless telecommunication system, this invention can not solve the problem of packet scheduling in wireless telecommunication system. The scheduling method used in wireless telecommunication is much more complicated than that in wire data telecommunication.
In order to meet the need of packet scheduling in wireless telecommunication, it is necessary to add the influence of channel condition on scheduling to the original packet scheduling method in wire data telecommunication. For example, US patent application 20020044527 “Channel efficiency based packet scheduling for interactive data in cellular networks” proposed a packet scheduling method used in GPRS system, which considered the influence of channel efficiency parameter on packet scheduling weight in connection with the commonly used weighted fair queuing (WFQ) scheduling method. The channel efficiency is the reciprocal of the maximum transmission rate permitted in the wireless condition, which represents the channel quality corresponding to each user, the better the channel quality is, the more the resource assigned to the packet is. This method is very efficient for the packet service without time delay sensitivity, but as for packet service sensitive to transmission time delay, it can not meet the requirements of service quality QoS. Because this method takes channel quality as the chief judging principle, the packet service with good channel quality takes less time in waiting for transmitting than the packet service with poor channel quality does. Therefore, the transmission of the service sensitive to the transmission time delay will be delayed due to its poor channel quality, and its QoS requirements will not be met.
There are also corresponding solving methods related to the specific packet services with time delay sensitivity. For example, US patent application 20030101274 “packet transmission scheduling technique” described a method for scheduling the real time packet service in WCDMA high speed downlink packet access HSDPA system, which judges the weight of packet by the maximum time delay threshold determined by the priority, quantity, time delay and service quality QoS of the packet on the basis of states of the wireless channel. The closer the time delay of data approximates to the maximum time delay threshold, or when the time delay is long enough, the higher transmission priority the data has. However, as for the real time packet service whose data delay exceed the maximum time delay threshold, its corresponding data packet will be discarded. The discarding of packet is unavoidable, and with the existing technique, the loss ratio of packet can not be further decreased, and there is no related solution provided for the users losing packet. As a result, the loss ratio of packet of the users in bad transmission condition remains high, and the communication quality and satisfaction of users may be influenced; Compared with wire transmission, the packet loss in wireless transmission often occurs in burst, so special measures are needed to deal with the packet loss.
The above methods only consider some of the characters of wireless telecommunication while neglect some others. For example, some of the real time packet services, such as the packet audio and video service, are quite sensitive to time delay jitter, which will greatly affect the quality of telecommunication. The common solution to this problem is to set data buffer with enough length to compensate the shortcomings of time delay jitter, as in US paten application 20030112796 “Voice and data exchange over a packet based network with fax relay spoofing” and US patent application 20030026275 “Dynamic Jitter buffering for voice-over-IP and other packet-based communication systems”. However, in order to control the big time delay jitter, big data buffer has to be set, which will result in the increasing transmission time delay of the date, which when exceeds a certain limitation, the requirement of service quality of wireless telecommunication can not be met. The existing technique does not consider the treatment toward the time delay jitter in packet scheduling under the condition of meeting all the requirements of service quality QoS, therefore the communication quality of some services is destroyed.